An asymmetric carbon atom by commonly accepted definition is a carbon atom containing four different radicals or atoms attached to it. Compounds which contain elements of molecular dissymmetry and compounds which contain one or more asymmetric atoms in the absence of a molecular center, plane or alternating axis of symmetry are known as chiral compounds. Chiral compounds can exist in two enantiomeric or mirro image forms also called optical isomers. Samples of chiral compounds which contain equal amounts of each enantiomer are known as racemic mixtures, but if such samples contain definite but unequal portions of each enantiomer they are called partially racemic, partially resolved or optically active. Fully resolved samples of chiral compounds which contain only one enantiomer are called optically pure.
The carbon atom of the carbonyl group in a ketone cannot be asymmetric because of the doubly bonded oxygen atom attached to it. Even if the two R groups of the ##EQU1## ketone compound are different, the carbon atom of the carbonyl group can only contain three different groups, the R, R', and the doubly bonded oxygen, and cannot be asymmetric. When the ketone is reduced to the secondary alcohol, ##EQU2## the carbon atom acquires four different groups attached to it, if R.sup.2 is different from R.sup.3 and neither R.sup.2 nor R.sup.3 is hydrogen. This creates a point of asymmetry in the alcohol. Many prior art methods for producing alcohols from ketones have nevertheless produced only racemic mixtures, because of their production of equal amounts of the two stereoisomers of the secondary alcohol. To obtain a preponderance of the desired enantiomorphic form of the alcohol, the mixture has to be separated into its optical components by inefficient and often expensive methods such as distillations, crystallizations and the like.